The present invention pertains to the MOS semiconductor art. Specifically, a buffer circuit for converting TTL logic signal levels to MOS logic signal levels is described.
In the MOS semiconductor art large scale integrated circuits are produced. Included among this class of semiconductor devices are MOS memories which are addressed through a plurality of address signals and the logical complement of these signals.
In many applications of memories and other types of circuit devices produced in the technology it is necessary to drive the circuit device from another type of semiconductor logic circuitry such as TTL. The TTL circuitry operates at different voltage levels providing a binary 1 at greater than 2.2 volts and a binary 0 at less than 0.6 volts. These logic levels are insufficient and in some instances incompatible with MOS logic levels.
Buffer circuits have been devised to provide conversion of TTL logic levels to levels compatible with MOS logic circuits. These are included in a 16K dynamic RAM, No. MK 4116, manufactured by MOSTEK which can be driven directly with TTL logic. The device is power efficient but requires three clocks to operate. The multiple clocks impose an undesirable speed limitation on the operation of the buffer and hence to the remaining circuitry connected with the buffer.
In an other type of RAM which interfaces with TTL logic circuits, manufactured by Hitachi as MH6147, a high speed static 16K RAM, the speed of the device is adequate. The power efficiency, however, suffers because of the d.c. current flow through an inverter in the device which receives the TTL driving signals.